Airless tires! Although they are pretty bad as tires, they're very durable, and you'll never, ever flat. If you don't weigh a lot, the wheels are durable, you avoid jumping off curbs, and hitting huge pot holes you should be fine mechanically. There's plenty of threads on them here. They're impractical for most people, since they're heavy, don't offer as smooth as a ride, and don't absorb road shocks as well, which is hard on rims. But for you, where changing a flat can be a complete nightmare, they might be worth it.

Total cost is nearly the same as a set of Marathon Plus and tubes. Some bike shops have the tool for installing them already, and charge a small labor fee, that would save 30-40 bucks.